1. Field of the Invention
This invention relates to a conjugated enyne derivative and a liquid crystal composition. More particularly, it relates to a liquid crystalline compound having a conjugated enyne group in its molecule and a liquid crystal composition.
2. Description of the Related Art
Display elements utilizing liquid crystals have been broadly utilized for watches, electronic calculators, etc. These liquid crystal display elements utilize optical anisotropy and dielectric anisotropy of liquid crystal substances. Liquid crystal phases include nematic liquid crystal phase, smectic liquid crystal phase and cholesteric liquid crystal phase, and display elements utilizing nematic liquid crystal among them have been most broadly applied to practical uses. Further, display modes applied to liquid crystal display include TN (twisted nematic) mode, DS (dynamic scattering) mode, guest.host mode, DAP mode, etc. as regards electrooptical effect. A number of liquid crystalline compounds including those which have been under a research step up to date have been known. However, no single substance which is filled in display elements and used has been found at present. That is, as liquid crystal substances expected as display element materials, those which exhibit liquid crystal phases within a temperature range as broad as possible, in the nature, around room temperature at which the substances are most often used particularly for display elements, are preferred, and also those which are sufficiently stable to the environmental factors and further are provided with physical properties enough to drive display elements, are required; whereas such a single substance satisfying these conditions has not yet been found. Thus, at present, several kinds of liquid crystal substances are blended or they are further blended with non-liquid crystal substances, whereby compositions provided with such characteristics have been prepared and applied to practical uses as the materials. Further, these liquid crystal compositions are required to be stable to moisture, light, heat, air, etc. under environment where they are used. Further, they are required to be stable to electric fields and electromagnetic irradiation. Further, it is required that the blended liquid crystal compounds are chemically stable to each other under the used environment. Further, the liquid crystal compositions are required to have suitable values of physical properties such as optical anisotropy value, dielectric anisotropy value, conductance value, etc. depending upon display modes and the shape of elements. Recently, in particular, the importance of substances having low optical anisotropy for materials of liquid crystal display elements of thin film transistor (TFT) mode has been increasing, as well as the importance of compounds having a high ratio of elastic constants (K.sub.33 /K.sub.11) for super-twisted nematic (STN) mode is increasing. Thus, in order to meet with such requirements, liquid crystal compounds as a single substance provided with various characteristics has been developed, but only inventions having improved some of these physical properties have been disclosed and no single material having solved all of the above-mentioned problems has yet been found. One of these disclosed inventions is that of Japanese patent publication No. Hei 1-502823 wherein compounds mentioned below containing cyclohexenylacetylene structure in the molecule thereof are claimed. However, concrete physical values of the cyclohexenylacetylene derivatives have not been disclosed, and it has been necessary to successively continue development of such new materials. ##STR2##